Three-hour train journeys between the central belt and London are on track following a pact between the UK and Scottish governments.
It would mean passengers from many parts of Tayside and Fife could get to the English capital within four hours.
The governments on both sides of the border have pledged to bring journey times down to three hours or under between Glasgow/Edinburgh and London.
The Scottish Government’s Infrastructures Secretary Keith Brown said: “This plan will bring to life our target of three hours or less for Glasgow and Edinburgh-London train journeys, which will lead to a significant move from air to rail, bringing big reductions in carbon emissions.”
He added: “We can’t afford not to build high speed rail. The main routes between Scotland and England are at capacity and the necessary improvements to address the capacity constraints on these existing routes would be substantial.”
The commitment from both governments was made alongside the publication of an HS2 report, which looks at options involving upgrades and new routes to hit the three-hour target.
New track could be built either side of the Pennines, or bypasses introduced on sections of the existing east and west coast main lines where speed is constrained, according to a report by HS2 Ltd.
The cost of the suggestions range from £17 billion to £43bn, although some improvements could be introduced in stages.
Those options with the best business case will be examined next year for implementation from 2019 onwards.
UK Government HS2 Minister Robert Goodwill said: “Together with the Scottish Government, we will be asking Network Rail to identify any options with a strong business case, for consideration for inclusion in future plans.”
The existing HS2 project, which is said to be worth £3bn to Scotland, will see journey times between London and Glasgow/Edinburgh reduced to around three hours 38 minutes by 2033. Earlier this month Virgin unveiled new trains that will cut Edinburgh-London times by 22 minutes, to four hours, in 2018.